Blood pressure irregularity sensing

ABSTRACT

A medical device obtains a set of data associated with a patient&#39;s non-invasive blood pressure cycle reading, provides a representation of a pulse interval map on the display screen based on the set of data, the pulse interval map including one or more interval data points representing intervals between heat beats, and alerts a caregiver if one or more of the interval data points fall outside an interval bound. The medical device can also plot a pulse volume map on the display screen based on the set of data, the pulse volume map including one more volume data points representing volumes associated with given heat beats, and alert a caregiver if one or more of the volume data points fall outside a volume bound.

RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application Ser. No. 61/355,919 filed on Jun. 17, 2010 and U.S. Patent Application Ser. No. 61/418,186 filed on Nov. 30, 2010, the entireties of which are hereby incorporated by reference.

BACKGROUND

A sphygmomanometer can be used to measure a patient's blood pressure in a non-invasive manner. In a typical example, a cuff is placed around the patient's arm and inflated. The cuff is deflated, and the blood starts to flow within the arm again. By monitoring the pressures at which the blood starts to flow (i.e., the maximum output pressure or systolic reading) and the pressure upon relaxation (i.e., the diastolic reading), an estimate of the patient's blood pressure readings can be obtained. Throughout the deflation of the cuff, arterial pressure changes cause pulsations or oscillations in the cuff pressure which have a correlation to the changing blood pressure in the underlying artery during a heart cycle.

SUMMARY

Embodiments of the present disclosure are directed to systems and methods for using data from a non-invasive blood pressure cycle to assist in the identification of heart irregularities. In example embodiments, such irregularities could include, without limitation, pulse interval, heart contraction, and heart output volume irregularities.

In one aspect, a medical device includes: a central processing unit (CPU) that is configured to control operation of the device; a display screen; and a set of one or more computer readable data storage media storing software instructions that, when executed by the CPU, cause the device to: obtain a set of data associated with a patient's non-invasive blood pressure cycle reading; provide a representation of a pulse interval map on the display screen based on the set of data, the pulse interval map including one or more interval data points representing intervals between heat beats; and alert a caregiver if one or more of the interval data points fall outside an interval bound.

In another aspect, a medical device includes: a central processing unit (CPU) that is configured to control operation of the device; a display screen; and a set of one or more computer readable data storage media storing software instructions that, when executed by the CPU, cause the device to: obtain a set of data associated with a patient's non-invasive blood pressure cycle reading; provide a representation of a pulse volume map on the display screen based on the set of data, the pulse volume map including one more volume data points representing volumes associated with given heat beats; and alert a caregiver if one or more of the volume data points fall outside a volume bound.

In yet another aspect, a method for estimating pulse irregularity includes: obtaining a set of data associated with a patient's non-invasive blood pressure cycle reading; plotting a pulse interval map on a display screen based on the set of data, the pulse interval map including one or more interval data points representing intervals between heat beats; alerting a caregiver if one or more of the interval data points fall outside an interval bound; plotting a pulse volume map on the display screen based on the set of data, the pulse volume map including one more volume data points representing volumes associated with given heat beats; calculating an integrated pulse volume based on the pulse volume map; and alerting the caregiver if one or more of the volume data points fall outside a volume bound, wherein the pulse volume map includes an upper bound and a lower bound represented by curves, a space between the upper and lower bounds representing a normal variation limits for pulse volumes, and wherein the device identifies beats falling within the space between the upper and lower bounds as representing beats with normal stroke volumes, and beats falling outside the space as representing irregular stroke volumes.

DESCRIPTION OF THE DRAWINGS

The present disclosure can be better understood with reference to the description below. Within the drawings, like reference numbers are used to indicate like parts throughout the various views. Differences between like parts may cause those like parts to be each indicated by different reference numbers. Unlike parts are indicated by different reference numbers.

FIG. 1 shows an example blood pressure cycle as measured by a non-invasive blood pressure device.

FIG. 2 an example physiological monitor device.

FIG. 3 shows example physical components of the physiological monitor device of FIG. 2.

FIG. 4 shows an example pulse interval map based on data collected from a blood pressure cycle.

FIG. 5 shows another example pulse interval map based on data collected from a blood pressure cycle.

FIG. 6 shows another example pulse interval map based on data collected from a blood pressure cycle.

FIG. 7 shows an example pulse volume map based on data collected from a blood pressure cycle.

FIG. 8 shows another example pulse volume map based on data collected from a blood pressure cycle.

FIG. 9 illustrates aspects of a portion of an example blood pressure cycle.

FIG. 10 illustrates additional aspects of a portion of an example blood pressure cycle.

FIG. 11 illustrates additional aspects of a portion of an example blood pressure cycle.

FIG. 12 illustrates additional aspects of a portion of an example blood pressure cycle.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to systems and methods for using data from a non-invasive blood pressure cycle to assist in the identification of heart irregularities. In example embodiments, such irregularities could include, without limitation, pulse interval and volume irregularities.

FIG. 1 illustrates an example blood pressure cycle 100 as measured by a blood pressure device. The blood pressure cycle 100 shows the measured pressures associated with the movement of blood through the patient's body, typically an arm. Specifically, the pulses shown are the variations in cuff pressure caused by changes in pressure within the underlying artery.

The timing of each heart beat 110 is shown on the X-axis in samples, and an amplitude of each heart beat 110 is shown on the Y-axis in mmHg×100. The spacing between adjacent heart beats 110 is referred to as the pulse interval.

FIG. 2 illustrates an example physiological monitor device 200. The device 200 generally assists the caregiver in gathering data associated with the patient, such as vital signs, etc. For example, in embodiments described herein, the physiological monitor device 200 is configured to take a patient's non-invasive blood pressure. The physiological monitor device 200 is also configured to interpret the patient's blood pressure reading and to identify potential heart irregularities.

In the example shown, the physiological monitor device 200 includes multiple health care equipment (HCE) modules. Each of the HCE modules is configured to measure one or more physiological parameters of a health-care recipient, also referred to herein as a patient. Example modules include a temperature measurement module, an SpO2 module, and a non-invasive blood pressure (NIBP) module.

The NIBP module connects to one or more peripheral NIBP components, such as an inflatable cuff that attaches to an appendage of a patient, such as an upper arm of the patient. The inflatable cuff is designed to measure the systolic and diastolic blood pressure of the patient, the mean arterial pressure (MAP) of the patient, and the pulse rate of blood flowing within the patient.

A front side of the physiological monitor device 200 includes a display screen 218. The display screen 218 is used to display physiological measure data obtained from the patient. For example, the patient's blood pressure and pulse rate can be displayed on the display screen 218. In another example, the blood pressure cycle 100 can be displayed. In addition, as described further below, data associated the irregularities detected using the NIBP data can be displayed on the display screen 218.

FIG. 3 illustrates example physical components of the physiological monitor device 200. As illustrated, the physiological monitor device 200 include at least one central processing unit (“CPU”) 308, a system memory 312, and a system bus 310 that couples the system memory 312 to the CPU 308. The system memory 312 includes a random access memory (“RAM”) 318 and a read-only memory (“ROM”) 320. A basic input/output system containing the basic routines that help to transfer information between elements within the physiological monitor device 200, such as during startup, is stored in the ROM 320. The physiological monitor device 200 further includes a mass storage device 314. The mass storage device 314 stores software instructions and data.

The mass storage device 314 is connected to the CPU 308 through a mass storage controller (not shown) connected to the bus 310. The mass storage device 314 and its associated computer-readable data storage media provide non-volatile, non-transitory storage for the physiological monitor device 200. Although the description of computer-readable data storage media contained herein refers to a mass storage device, such as a hard disk or CD-ROM drive, it should be appreciated by those skilled in the art that computer-readable data storage media can be any available non-transitory, physical device or article of manufacture from which the physiological monitor device 200 can read data and/or instructions.

Computer-readable data storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable software instructions, data structures, program modules or other data. Example types of computer-readable data storage media include, but are not limited to, RAM, ROM, EPROM, EEPROM, flash memory or other solid state memory technology, CD-ROMs, digital versatile discs (“DVDs”), other optical storage media, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by the physiological monitor device 200.

The physiological monitor device 200 also includes an input/output controller 322 for receiving and processing input from a number of other devices, including a keyboard, a mouse, a touch user interface display screen, or another type of input device. Similarly, the input/output controller 322 may provide output to a touch user interface display screen, a printer, or other type of output device.

As mentioned above, the mass storage device 314 and the RAM 318 of the physiological monitor device 200 can store software instructions and data. The software instructions include an operating system 332 suitable for controlling the operation of the physiological monitor device 200. The mass storage device 314 and/or the RAM 318 also store software instructions, that when executed by the CPU 308, cause the physiological monitor device 200 to provide the functionality of the physiological monitor device 200 discussed in this document. For example, the mass storage device 314 and/or the RAM 318 can store software instructions that, when executed by the CPU 308, cause the physiological monitor device to display various user interface screens.

Referring again to FIG. 1, the physiological monitor device 200 can obtain an NIBP cycle reading from the patient and, in some examples, display the blood pressure cycle 100 on the display 218 of the physiological monitor device 200.

In example embodiments, the physiological monitor device 200 can obtain an NIBP measurement using a traditional process during which a cuff is inflated to a pressure well above a patient's systolic blood pressure. The cuff is thereupon deflated, and the patient's systolic and diastolic pressures are calculated based on signals provide during the deflation. Other techniques can be used.

For example, the physiological monitor device 200 can obtain an NIBP measurement using fast blood pressure reflected wave technology as described in U.S. patent application Ser. No. 12/650,984 filed on Dec. 31, 2009, the entirety of which is hereby incorporated by reference. This application describes a method for determining the reflective wave attributes during a period when the pressure is held constant after the end of an inflation blood pressure cycle. During this measurement period the variations in those pulse attributes could also be measured and used to determine the variability of a patient's pulses.

In addition, the physiological monitor device 200 is programmed to analyze the data obtained from the NIBP cycle reading to assist in the identification of heart irregularities. Such irregularities can include, without limitation, pulse interval and volume irregularities.

For example, the data obtained during recording of the NIBP includes the pulse rate of the patient. This pulse rate information can be used to detect irregularities associated with pulse intervals.

Referring now to FIG. 4, a pulse interval map 400 is shown. The pulse interval map 400 is derived from the data obtained during the NIPB measurements. The pulse interval map 400 plots successive heart beats (X-axis) versus heart rate (Y-axis).

The pulse interval map 400 also includes an upper bound 412 and a lower bound 414 represented by lines. The space between the bounds 412, 414 represents the normal variation limits for a pulse interval. The placement of the bounds 412, 414 can be modified based one or more parameters, such as patient age, sex, height, weight, activity level, etc. The bounds 412, 414 can be calculated empirically using data from representative groups or can be measured through trials. For example, a study such as the Farmingham Heart Study or references like the American Heart Association or other sources can be used to set the bounds.

Alternatively, the bounds can be entered by the care giver as a percent variation from the mean. In the example shown, the caregiver provides information to the physiological monitor device 200 or the physiological monitor device 200 obtains information from, for example, an electronic medical record associated with the patient, to allow the physiological monitor device 200 to automatically set the bounds 412, 414 based on the obtained patient information.

A portion or all of the heart beats 420 measured by the physiological monitor device 200 during a NIBP cycle are plotted on the pulse interval map 400. For the example pulse interval map 400, all of the heart beats 420 falls within the bounds 412, 414 and therefore can be considered to be normal.

Referring now to FIG. 5, another example pulse interval map 500 is shown. In the pulse interval map 500, a plurality of the heart beats 510 fall outside the bounds 412, 414. In such a situation, the pulse interval map 500 may indicate that the pulse interval for the patient is irregular. In other words, the patient may have an arrhythmia or other irregularity associated with the patient's heart based on the irregular intervals between adjacent heart beats.

In one example, the pulse interval maps 400, 500 are displayed on the display screen 218 of the physiological monitor device 200 so that the caregiver can review the pulse interval maps when providing care to the patient. If one or more beats fall outside the bounds 412, 414, an alarm can also be provided to alert the caregiver of a possible irregularity. The pulse intervals that fall outside of the bounds may be highlighted using further indicia such as, for example, a different color or flashing the points.

In another example, the physiological monitor device 200 calculates the pulse interval maps 400, 500 and simply provides an indicator to the caregiver regarding whether or not an irregularity is found. For example, if all the beats are within the bounds, the physiological monitor device 200 can do nothing or provide the caregiver with an indicator such as a green icon or text like “Pulse Interval Normal.” Conversely, if one or more fall outside the bounds, an indicator such as a red icon or text like “Irregular Pulse Interval Detected” or “Additional Testing Recommended” can be displayed. In some examples, the caregiver can then click on the indicator to receive more information, if desired, such as the pulse interval maps themselves. Other methods of presentation and alert can also be used. These other methods include, but are not limited to, an audio playback in sounds of the heart beating, a video showing an audio and/or visual replay of the pulse information, and an animated representation of the data including a representation of a heart beating.

Referring now to FIG. 6, another pulse map 600 is shown. In the pulse map 600, the patient has exhibited a skipped beat 610 during the blood pressure cycle. When the physiological monitor device 200 detects such an irregularity, the physiological monitor device 200 can alert the caregiver of the same in one or more of the manners described above.

Referring now to FIG. 7, an example relative pulse volume map 700 is shown. The pulse volume map 700 is also derived from the data obtained during the NIPB cycle measurements. The pulse volume map 700 plots successive heart beats (X-axis) versus an estimate of the stroke volume associated with each of the heart beats (Y-axis). In example embodiments, the relative stroke volume for each beat can be estimated as the area under the curve associated with each beat 110. See FIG. 1.

The relative pulse volume map 700 also includes an upper bound 712 and a lower bound 714 represented by curves. The space between the bounds 712, 714 represents the normal variation limits for pulse volumes. Beats falling within the space between the bounds 712, 714 represent beats with normal stroke volumes, while beats falling outside the space represent irregular stroke volumes.

As before, the placement of the bounds 712, 714 can be modified based one or more parameters, such as patient age, sex, height, weight, activity level, blood pressure, etc.

A portion or all of the heart beats 720 measured by the physiological monitor device 200 during a NIBP cycle are plotted on the pulse volume map 700. For the example pulse volume map 700, all of the heart beats 720 falls within the bounds 712, 714 and therefore can be considered to be normal.

Referring now to FIG. 8, another example pulse volume map 800 is shown. In the pulse volume map 800, a plurality of the heart beats 810 fall outside the bounds 712, 714. In such a situation, the pulse volume map 800 may indicate that the pulse volume for the patient is irregular. In other words, the patient may have an arrhythmia or other irregularity associated with the patient's stroke volume. This irregularity can be expressed to the caregiver by displaying the pulse volume map 800 and/or providing one or more alerts.

In some examples, the data provided to the caregiver can be the raw data or represented as a percentage of the average. In some embodiments, the bounds (e.g., 412, 414 and 712, 714) can be tailored to the individual by dynamically calculating the bounds based on a signal to noise calculation. For example, the standard device could be divided by the mean to determine the outer bounds. Other configurations are possible.

One or both of the both timing and volume information can be combined or examined with additional information to provide enhanced information to the caregiver. For example, the interval and volume information can be combined to provide a better understanding of possible irregularities associated with a patient's NIPB data. In such a scenario, the interval and stroke volume data could be provided on a single map. The combination or relative severity of timing and volume variation can serve as a separate indication of abnormal heart function. For example, normal interval variation combined with abnormally varying volume data can indicate proper electrical function in the heart but improper filling or flow.

For example, in one embodiment, an expected envelop shape is plotted, and then the actual dots illustrating the patient's deviation, to the extend it exists, are plotted on top of the envelop. Other methods of presenting the data, including both numeric and graphical, can also be used.

Another example of data presentation includes the “normalization” of pulse volumes over different cuff pressures. During a blood pressure cycle the applied pressure in the cuff is varied systematically and there is an expected effect on the volume of the pulses that are induced in the cuff by the underlying artery in response to these different cuff pressures. For example, the pulsations that occur when the cuff pressure near mean arterial pressure are expected to be large verses the pulsations in the cuff when the cuff pressure is below diastolic or above systolic. Based on the measured systolic and diastolic blood pressures, the volume changes can be normalized using expected changes across different cuff pressures and only the deviation or residual from that expected curve can be plotted to be evaluated by the clinician for evidence of abnormal beat to beat volume variation.

Other attributes of the oscillometeric pulse can be measured and evaluated for beat to beat regularity. These attributes include:

-   -   integrated pulse volume (area under the curve for each         pulse)—see FIG. 9;     -   pulse ramp up time—see FIG. 9;     -   dichrotic notch position in time—see FIG. 10;     -   dichrotic notch position in amplitude—see FIG. 10;     -   area under the curve pre-dichrotic notch vs. post dichrotic         notch—see FIG. 11;     -   over all pulse time—see FIG. 11;     -   “dead space” between pulses—see FIG. 12;     -   Time position of reflected wave peak—see FIG. 12; and     -   Relative amplitude of reflected wave peak—see FIG. 12.

In some examples, the information regarding pulse interval, heart contraction, and/or heart output volume irregularities can be processed and presented to the caregiver directly on the physiological monitor device 200. In other examples, the data can be processed and/or displayed remotely, such as at a central monitoring station in a hospital or on a portable device such as personal data assistant (for example, an mp3 or other video-type could be rendered and played on the device). For example, the data can be sent to a central monitoring station in a hospital, and a nurse can review maps and alerts at a computing device located at the central monitoring station. Other configurations are possible.

Various embodiments disclosed herein can be implemented (1) as a sequence of computer implemented acts or program modules running on a computing system and/or (2) as interconnected machine logic circuits or circuit modules within the computing system. The implementation is a matter of choice dependent on the performance requirements of the computing system. Accordingly, logical operations including related algorithms can be referred to variously as operations, structural devices, acts or modules. It will be recognized by one skilled in the art that these operations, structural devices, acts and modules may be implemented in software, firmware, special purpose digital logic, and any combination thereof without deviating from the spirit and scope of the present disclosure.

Although the disclosure has been described in connection with various embodiments, those of ordinary skill in the art will understand that many modifications may be made thereto. Accordingly, it is not intended that the scope of the disclosure in any way be limited by the above description. 

1. A medical device comprising: a central processing unit (CPU) that is configured to control operation of the device; a display screen; and a set of one or more computer readable data storage media storing software instructions that, when executed by the CPU, cause the device to: obtain a set of data associated with a patient's non-invasive blood pressure cycle reading; provide a representation of a pulse interval map on the display screen based on the set of data, the pulse interval map including one or more interval data points representing intervals between heat beats; and alert a caregiver if one or more of the interval data points fall outside an interval bound.
 2. The device of claim 1, wherein the device calculates an integrated pulse volume based on a pulse volume map.
 3. The device of claim 2, wherein the pulse volume map includes an upper bound and a lower bound represented by curves, a space between the upper and lower bounds representing a normal variation limits for pulse volumes.
 4. The device of claim 3, wherein the device identifies beats falling within the space between the upper and lower bounds as representing beats with normal stroke volumes, and beats falling outside the space as representing irregular stroke volumes.
 5. The device of claim 1, wherein the device calculates a pulse ramp up time.
 6. The device of claim 1, wherein the device calculates a dichrotic notch position in time.
 7. The device of claim 1, wherein the device calculates a dichrotic notch position in amplitude.
 8. The device of claim 1, wherein the device calculates an area under a curve of the pulse interval map pre-dichrotic notch versus post dichrotic notch.
 9. The device of claim 1, wherein the device calculates a dead space between pulses.
 10. The device of claim 1, wherein the device calculates a time position of one or more reflected wave peaks.
 11. The device of claim 1, wherein the device calculates a relative amplitude of one or more reflected wave peaks.
 12. The device of claim 1, wherein the device provides a visual or audible representation of a recorded heart rate segment.
 13. The device of claim 1, wherein the device provides an indicator when pulse irregularity exceeds a predetermined level.
 14. The device of claim 13, wherein the predetermined level is set by a user.
 15. A medical device comprising: a central processing unit (CPU) that is configured to control operation of the device; a display screen; and a set of one or more computer readable data storage media storing software instructions that, when executed by the CPU, cause the device to: obtain a set of data associated with a patient's non-invasive blood pressure cycle reading; provide a representation of a pulse volume map on the display screen based on the set of data, the pulse volume map including one more volume data points representing volumes associated with given heat beats; and alert a caregiver if one or more of the volume data points fall outside a volume bound.
 16. The device of claim 15, wherein the pulse volume map includes an upper bound and a lower bound represented by curves, a space between the upper and lower bounds representing a normal variation limits for pulse volumes.
 17. The device of claim 16, wherein the device identifies beats falling within the space between the upper and lower bounds as representing beats with normal stroke volumes, and beats falling outside the space as representing irregular stroke volumes.
 18. A method for estimating pulse irregularity, the method comprising: obtaining a set of data associated with a patient's non-invasive blood pressure cycle reading; plotting a pulse interval map on a display screen based on the set of data, the pulse interval map including one or more interval data points representing intervals between heat beats; alerting a caregiver if one or more of the interval data points fall outside an interval bound; plotting a pulse volume map on the display screen based on the set of data, the pulse volume map including one more volume data points representing volumes associated with given heat beats; calculating an integrated pulse volume based on the pulse volume map; and alerting the caregiver if one or more of the volume data points fall outside a volume bound, wherein the pulse volume map includes an upper bound and a lower bound represented by curves, a space between the upper and lower bounds representing a normal variation limits for pulse volumes, and wherein the device identifies beats falling within the space between the upper and lower bounds as representing beats with normal stroke volumes, and beats falling outside the space as representing irregular stroke volumes.
 19. The method of claim 18, further comprising: calculating a pulse ramp up time based on the pulse volume map; calculating a dichrotic notch position in time based on the pulse volume map; calculating the dichrotic notch position in amplitude based on the pulse volume map; calculating an area under a curve of the pulse volume map pre-dichrotic notch versus post dichrotic notch; calculating a dead space between pulses based on the pulse volume map; calculating a time position of one or more reflected wave peaks based on the pulse volume map; calculating a relative amplitude of one or more reflected wave peaks based on the pulse volume map.
 20. The method of claim 18, further comprising: providing an indicator when pulse irregularity exceeds a predetermined level; and allowing the predetermined level to be set by a user. 